Method of making a printing surface



July 25, 1933.

C. W. BENNETT l METHOD 0F MAKING A PRINTING SURFACE Filed April 'A7, 1931 Casi' l f/ex/b/e cnaf/'ng Spec@ (gc/s :far/w09 Gas produc/'ng mder/'a/ Emu/sion C'. Wl'enne Inventor Patented July 25, 1933 UNITED STATES PATENT OFFICE CHARLES W. BENNETT, F DOUGLASTON, NEW YORK, ASSIGNOR,l RY VDIRECT .AND

MESNE ASSIGNMENTS, TO PHOTO-GAST, INC., 0F ROCHESTER,. NEW YORK, A CORPO- RATION OF NEW YORK METHOD 0F MAKING A. PRINTING SURFACE Application led April 7, 1931. Serial No. 528,435.

sheet is made, in a manner consuming less v time'and less expense and in a more efficient manner, than the methods used at present.

With these and other objects in view the invention resides in the novel steps and corntion,

. case if and binations of steps constituting the process as 'will appear hereinafter and be explicitly pointed out in the claims.

Referring to the accompanying drawin forming a part of this s ecifcation in whic like legends designate ike'parts` in all the views,

Fig. l is an enlaed sectional view illustrating a lplate pr invention;

Fig. 2 is an enlarged'sectional view illustrating the formation of a cast by Vgas evolution from the plate shown in Fig. 1; and

Fig. 3 is an enlarged sectional view illustrating the formation of a cast by mechanical separation of the plate from the body of the casting metal.

This invention constitutes an improvement in the art of producing relief printing'surfaces, this application constituting a continuation in part of my application for U. S. Letters Patent filed June 9, 1930 under the Serial No. 460,102 and entitled Method of printing. According to the present inventhe copy makeup is assembled in any convenient manner and the image of said copy then transferred to a supporting medium which preferably is a metallic plate.

The supporting medium further is preferably one so produced thereon with the plane of the characters in or substantially in the plane of the metal plate. That is to say, the characters in the image lie in a plane which may be the plane of the metal itself or a plane substantially parallel thereto, the latter being the when the plate is prepared with a coatingupon which the image is transferred. This will leave the spaces between the characters on the supporting medium in slightly relief relation which relief will subuced according y to this,

that the image of the copy issequently be increased` to a depth for the preparation of the'cast containin the printing surface and from Whichthe prmted sheet is produced.

The lspace between the characters just renecessary ferred to is covered with a material of measurincreased, and said material preferably comprises a heat insulating medium adapted to evolve a gas upon application of heat, for a purpose presently to appear. This gas .evolution may result from a chemical change taking place within the substance on the plate, or it may result from a chemical decomposition brought about` by heat upon a solid or a liquid applied to the external surface of the plate, inthe latter case the heat driving olf the occluded or absorbed as. This material may be for example, pow ered glass such as obtained from a Cottrell precipitator in the stack leading from a furnace burning powdered coal, sandfvarious metallic oxidesas for example, iron oxide, various metal salts as for example, copper, arsenate, cadmium oxalate, all of which have a relatively high melting point or at least a melting point well bove that of the metal of the printing surace. l

As an illustration, the copy makeup may be reproduced photographically in a camera.

upon a bichromated type sensitized surface of the supporting medium, as for example, aA copper plate. V

The plate is then coated with any suitable varnish such as kettle bodied linseed oil or any other sticky substance and, while sticky, dusted over with lany of the materials last mentioned and which are referred to as heat insulating, said `'dusting penetrating the sticky coating and the excess being brushed oftl or otherwise removed, after which the plate is'developed. That is to say, the material used asthe dusting medium willfnot be confined to the outer surface ofthe sticky varnish coating but will penetrate said coatable thickness which, as just stated, may be l roo l naturally would be repelled by the varnish,

l conveying the water throu at the temperatures of the -cast and this yet the dusting mediumv forms a means for h thefbody ofthe varnish, thuspermitting t e develo ment of the bichromated'platefevenafter it as been varnished. As a result of the development the parts of the material, carried b the plate and representing the characters o' the copy, will be washed-away thus leaving extending through the materialto the lane of the plate. In some instances it is desirable to cover or iiow over the surface of the def veloped plate a relatively thin film of a cem- 'cntitious or flexible material which may be anrubber compound such as from 2 to 6 ounces Para rubber dissolved in one gallon of solvent such as petroleum naphtha or benzol,` the .purpose being to assist not only in the adhesion of the metal of the printing surface to the metal ofthe supporting-plate, but also to assist materially in the subsequent formation of relief. -1

It has been found that a very eilicient manner offorming relief is by the creation of gas between the molten metal of the ultimate supporting plate when the cast is made. Therefore in the selection of the materials above referred to and which occupy the space on the supporting plate bef tween the charactersof the image, it is desirable to select those which will give off a gas cast. These temperatures will vary dependent on the particular metal of the cast, -but with an alloy having a melting point of approximately 70 C., there may be used the Cottrell precipitatexv above mentioned. The pouring temperature may7 vary from 100-400 C. If this gas e o ution were not controlled there would be a relatively uniformity of relief in the cast between all spacing between said characters, as a result of which the casted rinting surface would most likely become c oggedf with the printing ink. Therefore, the use of a film as above i indicated, applied over the developed plate,

practice provision should is highly instrumental in confining this gas evolution whereby the gas is held and relief l.is produced at Vthe same points,"which is the point of liberation. v

,The cast vwhich ultimatel contains the infany suitable manner, the aforementioned plate formfing. one side of the castin box. In actual e made to chill vthe metal of the plate so that when the molten casting metal, such for exampleas an alloy consisting of bismuth 50%, lead 25%, vtin 121/29,', and cadmium 121/2%, is iiowedfinto the mold, the ortion thereof forming the characters vof t e cop of the printn face of the cast, willy immediately c illed upon contact with the plane surface of said plate. For example printing relief has been obtained by subjecting the m'old said part-s characters regardless of thewith.

v a true plane,

plate Ito a cooling 4medium of substantialy' constant temperature. ca able of imparting' to said plate an inltial temperature of 5 C., the temperature of the poured metal being above 190 C. The heatinsulating material hereinbefore mentioned will serve to Aprevent a direct heat transfer from the plate to the molten metal and thus retard the chilling at those parts between the characters of the copy. It thus' results thatv the heat of the casting metal is delayed in reaching the time interval the heat of said casting metal is suiiicient to affect'4 the relief material on the plate and cause an evolution of gas therefrom. The pressure of this evolved gas pushes the molten casting metal away from the plane of the plate andthus creates an improved. relief. A peculiar feature' Ias well vls-important discovery is, that byA theevolution of this gas, the relief in the ultimate cast is made deeper or greater at those parts which correspondto greater separation of characters in the copy. After the lcast has cooled sufficientlyV -it is removed from the mold and is then ready for either direct prmting or may be used for the preparation of other plates;

It has been 'found also that high relief is obtained by utilizing a greater difference in temperature ofthe plate itself while the cast is being made. 4In other words, more gas is evolved if the plate is externally heated, while the casting metal is in contact therewith, and then subsequently chilled.

While the relief produced according to the abovemay' be sufficient for certain purposes, it may be found desirable to further increase this relief in the following manner. The

. plate may be prepared as above described or it may pulver-ized calcium carbonate as well as less bev prepared with materials such as finely divided materials previously mentioned, al1 of which do not givejoif as much gas as those mentioned and the coating of this material on the 4plate need not be necessarily of as reat thickness as in the preceding case. The lm of rubber may also be dispensed When the plateis thus prepared it is positioned to form a wall ofthe castingmold but preferably it is made tov assume the upper wall for a purpose as willbe readily appreciated from the following. The plate is ap plied tora frame or other holder which is adapted to maintain the plate in substantially a simple frame being a box of which'the plate is a cover, said plate covering plural openings iii the box vccuinectedwith a source of vacuum pressure. If an iron or steel plate is' used the'vacuum pressure would.

plate and during this delayed to utilize any means for maintaining the plate Further, revision is made ying ythe chilling the plate.

in a' true plane., in .the plate holder-for app medium to the back side' of The plate with its holder is thenapplied to the mold, preferably as the upper wall thereof and the molten casting metal flowed into the mold. Then the plate is chilled. As herein before pointed out, the molten metal in Contact with the metal of the plate atthose places corresponding to the characters of the copy,

the chilling of the plate, the metal of the cast correspondin to the printing surface is solidified an adheres to the plate. In the preparation of these casts it will, of course, be understood that the relationship of temperatures of the-chilling medium andl the casting Ametal will b e varied in accordance with the alloy of said metal. In other words for practical purposes it is believed that the temperature of the plate should not be greater sired, additional relief is obtained by a separation of the plate from the casting metal before the latter has completely solidified. When the plate is so separated the casting metal will adhere to the plate at the places of the characters so that the cast of the characters is withdrawn from the bod of the casting metal, but in this movement t e casting metal does not adhere to the spaces on the plate between the characters and therefore is not withdrawn. In practice a draw of as much as one quarter inch has been obtained which gives a remarkable relief.

The separation referred to may comprise a withdrawal of the plate. from the still molten casting metal and such withdrawal can be made to give an undercutto the characters in the ultimate cast. In other words, if'the plate is withdrawn rapidly relative to the chilling of the plate, undercutting results. With the usual practices of printing, however, this undercutting is not generally desired and therefore the withdrawal of the plate is made less rapidly, relative to the chilling, whereby'there results the ultimate formation of characters on '.the cast with the required slope'to the sides.v It is to be understood, of course, that the mass of the cast will be sufficiently cooled to be solidified before the plate is broken away from the cast, and this may be accomplished or expedited by a second chilling of the mold, but preferably the mass of the casting metal is not chilled until the proper relief is obtained through the withdrawal of the plate. lThe will be chilled first, and' by proper control of the 4casting metal and face of the vmold was fil adhesion of the printin to the plate may be varied through the utilization of various films or coatings over the' entire surface, as above mentioned.

The principles of the above may likewise be utilized in a reversal of the operation. In other words, after the mold is filled with molten metal, the plate need not be withdrawn but, after the" initial chilling and solidification of the printing surface of the cast, a portionof ino ten metal may be withdrawn from the' mold and accomplish the same result of increased relief. From these withdrawals either ofthe plate, or the metal,

it will thus be seen lthat heat is withdrawnfrom the molten metal by conduction throughv the characters themselves and therefore the amount of Vrelief formed is self adjusted.,

Where 'the characters are close together heat is withdrawn at a relatively more rapid rate than where the characters are far apart. This means that where the vcharacters are close together the cooling will go forward to the point of brid ng across between the characters with solidified metal earlier than in the case where the characters are further apart.

In otherl words, a further withdrawal of molten metal will occur 'in the case where the characters are further apart than where they are close together,v thereby yielding more relief in the former case than in the latter, thus rendering the process a means of obtaining very high relief where this is required and adjusting itself automatically downward where high relief is unnecessary. It is obvious that the plate may assume the position of one of the vertical sides of the mold when the casting metal is run into the mold so that any gas would not collect against the plate, after which and when the ed, the mold could be turned for the plate to assume-the upper wall thereof,

and then the plate chilled, In cases where the castin metal was withdrawn from the late it mlght be necessary'to provide a vent surface of the cast- 1n the upper part of the mold so that the metal would leave the plate except at the characters thereon, such a vent of course,

being controlled for opening at the proper time namely, after the initial chilling ofthe character forming portion of the cast.v

Through such a vent a1r or gas of atmospheric or su ratmospheric pressure may be admit as the exigencies demanded.

It is obvious that those skilled in the art may vary the details of construction and arrangements of parts constituting the apparatus as well as the steps and combinations of steps constituting the method, all within the s lrit of the invention, and therefore it is'- not esired to be limited to the foregoing except as may be required by the claims.

What is claimed is 1. The method of producing a relief printing surface which consists in chilling to solid- .metal, said .ification selected portions of a mass of molten metal; and raising said portions to lobtain the desired relief. Y A

2. The method of producing a relief printin surface which consists in chilling to so idiication portions of a mass of; molten portions corresponding to the characters to be printed; and raising said hzracter portions to obtain the desired re- 3. The method of producing a relief printing surface which consists in c illing to solidii'cation ina mold portions of a mass of molten metal, said portions overned by contact with a preformed mo d surface; and raising said portions to obtain the desired relief.

e 4. The method of producin ing surface which consists in c ,illing to solidication in a mold portions of a mass of molten metal, said portions governed by contact with a preformedA mold surface; and raising said portions by movement of the mold surface to obtain the desired;relief.

5. The method of producing a relief printing surface which consists in chilling to solidification in a mold portions of a mass of molten metal, said portions governed by cona relief printtact with a preformed mold surface; and

raising said portions with respect to the center of gravity of the mass of metal to obtain the desired relief, saidraising accomplished by the lowering of the said center of gravity.-

6. The method of producing a relief printing surface'which consists in chilling to solidification through a preformed plate portions of a mass of molten metal; and raising said portions to obtain the desired relief, said raising accomplished by movement of said p ate.

7. The method of producing a relief printing surface which consists in bringing a mass of molten metal into contact with a. plate having thereon reproduction of the characters to be printed; said reproductions formed by bare portions of the plate and portions covered by a gas producing substance; and

.causing relative movement between said plate and the mass of molten metal to obtain the desired relief in the casts of the printing characters, said movement brought about by the evolution ofgas from said substance.

8. The method of producing a relief printing surface which consists in bringing a mass of molten metal into contact with a plate having thereon reproductionsof the characters to be printed; chilling said plate to solidify the portions of the molten mass in contact with .said reproductions; and causing relative movement between the chilled plate and the mass of molten metal. to obtain 'the desired relief in the casts of the printing charv acters.

9. The method of producing a reliefV printing surface which consists in bring a mass of Vmetal in contact with to be printed; chilling said plate to solidifythe portions ofthe molten mass in contact with said reproductions; and moving the said plate relative to the mass of molten metal to obtain the desired relief in the casts of the printing characters.

` 10. The method, of producing a relief printing surface which consitsill bringing a mass of molten metal into molding contact with a plate having thereon reproductions of the characters to be printed; chilling Said plate to solidify the portions ofthe molten mass in contact with said reproductions; and withdrawing from the mold a part of the mass of molten metal to obtain the 'desired Vrelief in the casts of the printing characters.

tions of said plate and the body of said met-al by gas evolvedfrom the covered portions while the metal is contacting the bare portions of said plate.

12. The method of producing a relief printing surface which consists in establishing a. plate having bare and covered portions; casting-a printing metal on said plate; and causing a separation between said plate and the body of said metal by movement of said plate While the metal is contacting the bare portions of said plate. A

13. The method of producing a relief printing surface whichonsists in establishing a plate having bare and covered ortions casting a printing metal on said pliite; and causing a separation between the covered portions of said plate and the body of said metal by movement of the body of said metal while the metal is contacting said plate, said movement brought about by pressure of the gas evolved from the substance on the coveredortions of said plate.l

14. The method of)V producing a relief printing surface which consists in obtaining V-an image of the copy makeup on a plate, the

characters of theV image appearing as bare metal, the spaces between the characters treated with a material capable of evolving gas when heated; and casting the printing metal in contact with said image whereby the heat o f the metal will cause an evolution of gas the pressure of which will produce increased relief ofthe casted characters.

15. The method of producing a printing surface which consists in photographically producing upon a copy makeup; applying to said image a coating capable of evolving gas when heated; removing said coating from the character portions of said image; and casting the printing the treated image the bare portions oi plate an image of the los whereby the heat of the metal will cause an evolution of gas the pressure of whichwill produce increasedfrelief of the casted characters.

16. The method of producing a relief printing surface which consists in establishing a plate having bare and covered portions, the coating on the covered portions capable of evolving gas when heated; and casting therefrom the printing surface in which the relief is greater than the relief of the plate the diierence in amount of relief brought ils ' las 

